1. Field of the Invention
The present invention relates to a color thermal printer and color thermal printing method. More particularly, the present invention relates to a color thermal printer and color thermal printing method in which the entire surface of color thermosensitive recording material after recording can be fixed and bleached.
2. Description Related to the Prior Art
A direct type of a color thermal printer is known in the field of thermal recording, and is operated to record a full-color image in a three-color frame-sequential method. A full-color thermosensitive recording material of a direct recording type is used, which includes a support, a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer and a yellow thermosensitive coloring layer. The yellow coloring layer among those has the highest heat sensitivity. The cyan coloring layer has the lowest heat sensitivity. Three-color images are recorded in the order of yellow, magenta and cyan. In order to avoid further coloring of the yellow coloring component in the course of the magenta recording, a yellow fixer lamp emanates visible violet rays or near ultraviolet rays in a wavelength range peaking at the wavelength of 420 nm, and fixes the yellow coloring layer of the recording material. In order to avoid further coloring of the magenta coloring component in the course of the cyan recording, the magenta fixer lamp emanates ultraviolet rays in a wavelength range peaking at the wavelength of 365 nm, and fixes the magenta coloring layer. As unrecorded regions on the recording material defined around the full-color image has a very light yellow-greenish color, the magenta fixer lamp is driven after the cyan recording to apply rays to all the unrecorded portions to bleach them.
The direct type of the thermal recording has an advantage in that no ink ribbon is used, in contrast to the melt-type or wax transfer type of thermal transfer printer. The direct type does not have any mechanism for feeding ink ribbon, and is mechanically simpler. However the set of the fixer lamps is required for fixation of the yellow and magenta coloring layers.
If the thermal printer has the fixer lamps disposed higher than the recording material, the entire surface of the recording material can receive application of fixing rays. But if a thermal printer has the fixer lamps disposed lower than the recording material, the thermal printer requires guide members for supporting the recording material in contact with its lower surface. The guide members have shapes for supporting only lateral sides of the recording material as viewed in the width direction, for sufficient fixation. Unfixed regions in a belt-shape remain on the lateral sides of the recording material after the recording material is fixed in passage through the guide members. If it is desired to bleach the unfixed regions, an additional ultraviolet lamp must be used for bleaching the recording material having been conveyed out of the guide members. The requirement of the additional lamp is unadvantageous, as it is inconsistent to the small cost and the structural simplicity.